cardio

Anyone have a good recommendation for a cardio routine? I heard doing more than 20 minutes a day can actually be detrimental cuz you lose muscle along with the fat... also should it be done every day or just a couple times a week?

When cutting, I do cardio 5 X a week. Right after I wake i take 5 gm glutamine, then hit the cardio for 45min-1hr. Right after cardio I have a doub protein shake + tablespoon flax oil...When not on cutting diet I try to do cardio 3x week for 45 min.